Combustion gas heater apparatus for multitemperature air supply for furnaces



Dec. 18, 1951 J CRUlSE 2,578,783

COMBUSTION GAS HEATER APPARATUS FOR MULTITEMPERATURE AIR SUPPLY FOR FURNACES Filed Feb. 5, 1948 2 SHEETSSHEET l Gas '13 Bur gr Fig. l.

INVENTOR.

John H. Cruise BY MAM W Dec. 18, 1951 J. H. CRUISE 2,578,783

COMBUSTION GAS HEATER APPARATUS FOR MULTITEMPERATURE W AIR SUPPLY FOR FURNACES Filed Feb. 5, 1948 2 SHEETS-SHEET 2 Air to Gas Burner Patented Dec. 18, 1951 UNITED er -Ares COMBUSTION ,GAS 'HEATER APPARATUS FDR-JMULTITEMPERATURE AIR SUPPLY f FOR FURNACES :JJOhniHQCruise,ELimlen, Nail; assignonibyrrmesne assignments, to-Combustion Engineering-c superheater, Inc., -a;;corporationt of Delaware Application-February 5, reis;--seriarnozers9 I azheatin medium fOI'RtheaaiI for. combustiomand @With :the: accompanying drawingsrwherein 2' Figure 1;:is a:diagrammaticwverticfl sectional view.;of an :air heater rassociate'd-swith; a -steam generator provided with. :two a separate :Jburning .smeans ,forhurning separate fuels;

Figure 2 ;is .:a transverse section rof thew-air :heaterssimilar ;to Figure :1, i-takenron :line i2- -'2 10f Figure 4;

Figure ,3 :is .a ha1f:,section,-;of ::the air iheater taken-V on line :3-3 of Figure 1.2; "and ure .4 visfl-arhalf n elevation 'of. the air i heater E'- tviewed :from line ;4-=-:41of :Figures 1 l and L2.

i The illustrative: syst m representedzbylE igur-e 11 :includesa furnace I included;intheisteamc'genen ator there: shown. 1 A :first: fuel, :such :as iGOkBLOI ;;the like, is fired in:this1furnaceleithenomartraveli s rategstoker 2:,or :111 other ;conventiona1: manv.ner; while :a second:fue1,rsuch as :gas b1astrf1lr- :or other)-, is delivered 317.0 the ;furnacei :by mmeanseof burner ;3. Associated with z thegfurnace .is ,boflermof @well v-knownrconstruction :having top and {bottom drums: 5383161 interconnected bysza Joankof tubes I. Baflles :8, c9 {and [0 direct ;gases leaving the furnace :downwardlwand then upwardly [through the boiler. 'sAn,Ofita k.e1 idisrects the flue gases ithroughcrcthe rhreechin-g Z1110 ithe ,toppf :thei.-,air:iheater 1L3 swhenoegthejeases nassdownwardly. through-the ztubeszof tubeehank ,lmandJeavethe,air{heaterzatgthe bottomnfssaid :tube'bank through flue 11.5. I

rue! forgthe Stoker 52;.is deliveredathrough 5-4 Claims. (omit- 56) V hoppersHi4onxto-ttheitraveling grate;anjd the ;blast furnace: :gas isv delivered term 1 burner :3, via, duct [1; The duct lladjacentxthefurnacevwalllisenclosed by: an air chamber .18 through which'preheated air for combustion from theairheatergis delivered into the furnace via-conduit El'9.cAir for combustion to the stoker12 .is-deliveredt from the air heater l3 through conduit ';20;to the.:air

compartmentsi2a 'ofithe stoker.

Asillustratively shown in Figures l-2-3'4,'-the air heater 13 comprises an enclosure includin front andrear wa11s'2 I and 22, end-walls 23:anfi "top and bottom' walls 24 *and i 25. The top and bottom walls include tube sheets-26 amt-21 which extend for the full width ofithesair=heaterzbe- :tween the endwalls 23 but are spacedfrom the front and-rear walls '2 l and 22 (as Figure 2 indicates). A bankof tubes M for flue gas conduction are fastened into the tube plates andllike wise extend for the full width of the air-heater between end-wa11s 23 (see Figures 3-4) A and are spaced 'from the frontsand rear'walls 2| and =22 (see-Figure 2).

'Spaced transversely of the tube bank-arebafiles 28, 29 and-3U. Top baflle 28-extends from the front wall TH and across the tube bank l4. Gen-- tral bafile 29 extendsifrom the rear wall .22-across the tube .bank hi and stops .in alignment-with :the front wa1lt'2i. Lower baffie 3|] extends from the front wall across the .tube bank I14. Between :bafiles 28 and 370 there is ancopeningprovided in .:the front wall 2 l towhich is connected-a duct 8| through which. theair to beheated is directed into the air heater. This .air supplyduct is-best shown in Figure 2. I

:One of theheater end wallsv23is provided with :an opening ,32 to which thesconduit I9 is conhectedfor. conveying air to the blast furnacegas burner 3. This end wall 23 is furtherprovided withrgan opening 33 to vwhichatby-pass conduit :34 -isrconnectedz=for conveying. heated :lairiintothe conduit :19 (see .Eigure 11) :Jeading-toxtheeas burner,-3. Th,e;heater?s bottom wallufi is pro- :vided with :an opening 35 to i which; is :connected {the conduit, 2 ll :(again see'Figure for; delivering .heated air for combustion :torthe:stokeri 2. 1=A by :.pass.damper;36 is provided inbaflle1-30;(se.e;l igures 1-2) for short circuiting air deliveredztoithe :air heatergfrom duct 3i directlyxinto :condult;;20. -Conciuit2llisrprovitied with damper-5:1,. :Conduits ta-sand 534, 13,136 provided iWit'h ;;dampers ifi'lmandtiw respectively. Y 1 V g laiilnvtoperationithe hotzgases from therbreeching 2' :passrdownwardly :xtthrough the ntubes of aair heater zztubez-zhankri l 4;;and .out through flue iii.

The hottest gases therefore pass through the upper portion of the air heater and the cooler gases through the lower portion. Air for combustion enters the air heater via duct 3| and is divided by partition 29 into an upper and lower portion. The upper portion passes transversely across the tube bank l4, thence upwardly in the chamber between the tube bank and rear wall 22, thence transversely of the tube bank into the 01?- take chamber 32 between the tube bank and the front wall 2| and thence via conduit l 9 to the gas burner 3.

The lower portion of the air passes transversely across the tube bank, thence downwardly in the chamber between the tube bank and the rear wall 22, thence transversely back across the tube bank into the offtake chamber 33 between the tube bank and the front wall 21 and thence into the conduit 20 to the stoker. Should the stoker air become too warm it may be tempered by opening damper 36 and admitting some of the cooled air directly into the heated air below.

As described, the air heater is designed in two sections, an upper and lower section. Within the upper section the air flows generally upwardly in counterfiow to the downward gas flow and in the lower section the air flows generally downwardly in parallel flow to the gas flow. The

air for combustion to the gas burners is passed over the tubes of the upper section containing the greater amount of heating surface and thereby reduces the heat carried by the gases to the lower section, The air temperature obtainable from the lower section is thereby held to a limit permissible for operation of stoker 3. The

air temperature leaving the upper section for the gas burner 3 is relatively high, the burner construction being such as to permit a high tem perature.

When burning both blast furnace gas and coke at the same time, in any proportions of these fuels, the air heater is so proportioned that the air temperature leaving the lower section will not exceed the safe limit for the stoker. Moreover, when coke alone is being burned, the rating of thesteam generator is such that the flue gas entering the air heater is reduced to the temperature where the air for combustion from the heater is again 'at a temperature safe for use in stoker operation.

' It is possible to obtain a substantially greater steam output from the steam generator when burning gas than when burning coke and it may be desirable to obtain higher ratings than those designed for when burning blast furnace gas alone. The limiting element for such higher ratings is the static pressure developed by the forced-draft fan (not here shown) for supplying the furnace I with air for combustion by way of heater I3 and inlet duct 3!. Under these circumstances some of the air for combustion to burner 3 may be directed through the lower portion of the air heater and thence carried via conduits 34 into conduit [9 and thence to the gas burner. In this case the damper 39 in conduit '34 will be opened and the damper 31 in conduit 20will be closed so that no air will pass to the stoker.

' By thus directing the air through the air heater [3 through both the upper and lower sections thereof, the flow area for the air is materially increased and consequently the resistance to flow materially reduced. This reduces the pressure against which the forced draft fan is obliged to operate and thereby increases its capacity and therewith the rating of the steam generating unit.

While the preferred embodiment of my invention has been shown and described, it will be understood that changes in construction, combination and arrangement of parts may be made without departing from the spirit and scope of the invention as claimed.

. I claim:

1. In a heat exchanger, the combination of a chamber, a plurality of conduits extending lengthwise therethrough, means for flowing a heating gas through said conduits from the gasentering or high-temperature end of the chamber to the gas-exit or reduced-temperature end thereof, a plurality of bafiles spacedly positioned between the two chamber ends to form within the chamber a plurality of transverse passes serially extending back and forth across the exterior surfaces of said conduits, an inlet duct for directing air to be heated into each of an intermediate pair of said transverse passes remote from the transverse passes at the extreme chamber ends and substantially midway therebetween along the conduit lengths, partition means between the two passes in said inlet pair for causing a portion of said incoming air to flow from said intermediate inlet through a first series of chamber passes leading to said high-temperature chamber end and another portion of the incoming air to flow from the inlet through a second series of chamber passes leading to said reducedtemperature chamber end, a first outlet duct'connected to the extreme-end pass at said high-temperature chamber end to take therefrom air that is heated to the highest temperature, a second outlet duct connected to the extreme-end pass at said reduced-temperature chamber end to take therefrom air that is heated to a lower temperature, and means for at times by passing a portion of the lower-temperature air from said second outlet duct into the high-temperature air in said first outlet duct.

2. In a heat exchanger, the combination of a chamber, a plurality of conduits extending lengthwise therethrough, means for flowing a heating gas through said conduits from the gasentering or high-temperature end of the chamber to the gas-exit or reduced-temperature end thereof, a plurality of baflles spacedly positioned between the two chamber ends to form within the chamber a plurality of transverse passes serially extending back and forth across the exterior surfaces of said conduits, an inlet duct for directing air to be heated into each of an intermediate pair of said transverse passes remote from the transverse passes at the extreme chamber ends, partition means between the two passes in said inlet 'pair for causing a portion of said incoming air to flow from said intermediate inlet through a first series of chamber passes leading to said high-temperature chamber end and another portion of the incoming air to flow from the inlet through a second series of chamber passesleadjing to said reduced-temperature chamber end, a first outlet duct connected to' the extreme-end pass at said high-temperature chamber end to take therefrom air that is'heated tothe highest temperature, a second outlet duct connected to the extreme-end pass at said reduced-temperature chamber end to take therefrom air that is heated to a lowertemperature, a by-pass conduit interconnecting said first and second outlet ducts, and dampers in said ducts and in said conduit for independently regulating the flow of air through said first and second series of chamber passes and through the by-pass conduit.

3. In a system comprising a furnace that is provided with a gas burner and a stoker for respectively burning in the furnace a gas and a solid fuel either simultaneously or separately, the gas burner delivering combustion air to the gas at a temperature higher than the combustion air delivered by the stoker to its fuel, an air heater having tubular elements, a flue connecting the furnace offtake to the tubular elements for the flow of hot gases therethrcugh from the hot or gas entrance and to the cold or gas exit end, and a heat exchange casing for combustion air to be heated enclosing said tubular elements and extending longitudinally thereof, the combination of a partition located generally centrally of said tubular elements and extending transversely thereof within said casing to divide the casing into a high temperature heat exchange compartment adjacent said hot or gas entrance end of the tubular elements and a low temperature heat exchange compartment adjacent said cold or gas exit end of the tubular elements, air inlet means for admitting the aforesaid combustion air to be heated into said casing adjacent said transverse central partition and on both sides thereof whereby the admitted air enters both of said compartments adjacent the partition location longitudinally of the tubular elements and thence flows through those compartments in two separate streams, means forming a heated air outlet from said high temperature compartment of the casing and another heated air outlet from said low temperature compartment which two air outlets respectively are located adjacent the hot or gas entrance end of said tubular elements and adjacent the cold or gas exit end of those elements, a first conduit connecting the air outlet adjacent the hot end of the elements to the gas burner, a second conduit connecting the air outlet adjacent the cold end to the stoker, a by-pass conduit interconnecting the first and second conduits, and dampers in each of the aforesaid conduits for independently regulating the flow of air from the heaters hot end outlet to said gas burner and of air from the heaters cold end outlet to said stoker and of air from the cold end outlet to the hot end outlet through said by pass.

4. In a system comprising a furnace that is provided with a blast furnace gas burner and a traveling grate stoker for respectively burning in the furnace blast furnace gas and coke either simultaneously or separately, the gas burner delivering combustion air to the gas at a temperature higher than the combustion air delivered by the stoker to the coke, an air heater having tubular elements, a flue connecting the furnace offtake to the tubular elements for the flow of hot gases therethrough from the hot or gas entrance end to the cold or gas exit end, and a heat exchange casing for combustion air to be heated enclosing said tubular elements and extending longitudinally thereof, the combination of a partition located generally centrally of said tubular elements and extending transversely thereof within said casing to divide the casing into a high temperature heat exchange compartment adjacent said hot or gas entrance end of the tubular elements and a low temperature heat exchange ccmpartment adjacent said cold or gas exit end of the tubular elements, air inlet means for admitting the aforesaid combustion air to be heated into said casing adjacent said transverse partition and on both sides thereof whereby the admitted air enters both of said compartments adjacent the partition location longitudinally of the tubular elements and thence flows through those compartments in two separate streams, means forming a heated air outlet from said high temperature compartment of the casing and another heated air outlet from said low temperature compartment which two air outlets respectively are located adjacent the hot or gas entrance end of said tubular elements and adjacent the cold or gas exit end of those elements, a first conduit connecting the air outlet adjacent the hot end of the elements to the gas burner, a second conduit connecting the air outlet adjacent the cold end to the stoker, a dampered bypass between the heaters said air inlet and the air outlet adjacent the cold end, a by-pass conduit interconnecting the first and second conduits, and dampers in each of the aforesaid conduits for independently regulating the flow of air from the heaters hot end outlet to said gas burner and of air from the heaters cold end outlet to said stoker and of air from the cold end outlet to the hot end outlet through said by pass conduit and of air from said heaters inlet to said cold end outlet.

JOHN H. CRUISE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,514,785 Owen Nov. 11, 1924 1,812,458 Turkus June 30, 1931 1,819,174 Jacobus Aug. 18, 1931 1,825,884 Mueller Oct. 6, 1931 1,973,697 Bailey Sept. 18, 1934 FOREIGN PATENTS Number Country Date 18,510 Netherlands Aug. 15, 1928 

